Well apparatus



June 10, 1958 H. u. GARRETT ET AL WELL APPARATUS 7 Sheets-Sheet 1 Filed Sept. 16, 1955 Henry U. Gar/ref! Norma/7 E Eran n HVVENTURS June 10, 1958 H. u. GARRETT ET AL WELL APPARATUS Filed Sept. 16, 1955 7 Sheets-Sheet 2 4/ Mia f 7% n0 0 fN v m r 1 05 5 Q uF Mi W 0/ 0d r m w l H w w T 7 aw 2 6 i Hwfi66 5 7 5 (1U 5 7 ATTORNEY.

June 10, 1958 H. UAGARRETT ET AL 2,838,005

WELL APPARATUS Filed Sept. 16, 1955 '7 Sheets-Sheet 3 fien/"y (X 60/79 f2 Norma/7 /T 5/0 W/7 INVENTORJ BW Wi ATTOR/VEVJ June 10, 1958 H. u. GARRETT ET AL 2,338,005

' WELL APPARATUS Filed Sept. 16, 1955 7 Sheets-Sheet 4 INVENTJORS BY f 2%? W ATTOR/VEVJ June 10, 1958 H. u. GARRETT E1- AL 2,838,005

wzu. APPARATUS Filed Sept. 16, 1955 7 Sheets-Sheet 5 BY M W ATTORA/[VJ H. u. GARRETT ETAL 2,838,005

June 10, 1958 WELL APPARATUS Filed Sept. 16, 1955 7 Sheets-Sheet 6 ATTOR/VLVJ June 10, 1958 H. u. GARRETT ETAL WELL APPARATUS Filed Sept. 16, 1955 '7 Sheets-Sheet 7 INVENTORJ ATTORA/[VJ 2,838,605 Patented June 10, 1958 [ice (aesaess WELL APPARATUS Henry UaGarrett andNormau F. Brown, Longview,

Tex., assignors, bymesne assignments, to U. S. Indus- "tries, Inc., a corporation of Delaware Application September '16, 1955," Serial Fla-534,727 :26 Claims. (Cl. lii352) This invention relates to improved 'freepistons of the type which are'moved upwardly through a well cone-duit wby'fiuid flowing therein and then drop down the c-onduit'toperform various functionstherein- In one I employing the pistons "wherein"improvedmechanisms are 1 of its-aspects; it relates to free pistons and'to'well systems provided todetermine or aidinthe determination of the extent of movement of the free pistons in the well. 'In

a broadera'spect, the invention relates to improved latching mechanisms for controlling a motor-driven move- .mentbetween two parts of a well apparatus.

. Free pistons. are becoming" ofincreasing popularity in performingor-aiding in-theperforniance of a number of 'well operationsincludin' -gas lifting, parafiin removal from tubing, and others. 11 general, the mode of. operation of a freepiston'involvesdropping it down a tubing while permittingfluid in'the; tubing tofiow throughor around the pistonand then, after the piston reaches its lower level in the tubing to cause it toform a substantially imperforate .plug in 'thetubing so that it can be moved. upwardly by fiuid-fiowin the: tubing.

7 i a In order to actuate thefree=piston as above'outlin'ed, it is provided with'one of, or preferably both, an expans'ible packer .anda valve -adapted to close a flow I passageway.by-passing the packer.

sion of .the packer .to form a-slidingseal with the tubing Then lupon expanuated at the-.well head-asadescribedrin our'cope'nding with. It can also be derived from aperature responsive devicearrangedso that as the piston application Serial No.'-534,728;'filed of 'even data herepressure or a temv.;travels.up and down the atubing,-ithe-:device is exposed Ito,.a change in well-pressure" ordevelop forceto; expandand contract-thevpacker' and temperature to thereby to open and close the va-lve. i In any case movement of the valve between open and closed position and equally 1 movement of the packer between: expanded-and contracted position must not takeplace-rin such a manner that a midway condition-in-which all forces tendingto (open andclose th'e valve,- or toexpand orcontract the s packer,

are" in equilibrium might be 1 reached, automatically maintained, and stop the free-pistonfrom' traveling. Where a change in wellvtemp'erature" orpressure is employed togenerate forcte --for actuating the free piston,

; it will be noted =-that the change in-iemperature or pressure bears a'generally 'liiiear relationship to well depth and with respect to afree piston traveling up and down the-well bore, occur; gradually.

r E; It:-is-accordingly 'mecessary that force generated by such change be accumulated, as the =free piston-m'o'ves,

,bu,t*-prevented* from -becorning "effective' to' actuate the met. The force isthen released to actuate the free piston decisively; that'is; once the actuation of the free piston begina'theacttiation will be positively and defi nitely completed.

#freepiston -until' certain? predetermined conditions are I ":While actuation of the free piston to permit it to reverse itsdirec'tion of travel'at the lower end of its stroke can occur, inmany instances, at indeterminate conditions in respect of'pressure, temperature, depth in a well, time, etc.,- and still be satisfactory, the'reversal at the upper end'of its stroke should not occur before and mustnot-fail upon-the free piston reaching such upper end even though there may be irregularities or variations in temperature-or pressure at the well head.

Thus, in manyinstances, free piston reversals at the lower terminus may satisfactorily depend upon effects which need notbepr'ecise or consistent, but the 'reversal'at the upperte'rminus must depend upon the free piston positively reaching thewell head or other predetermined upper location in the well. While well head apparatus has been provided for positively causingthe piston to be placed in condition to reverse its stroke after it has reached the upper terminus, such apparatus is normally'relatively expensive and in many instances, it would be desirable to avoid using it.

It istherefore a general object of this invention to provide a well system and a free piston for use in such a system wherein the power required to operate the piston to either permit or prevent fluid to bypass the sameas it moves through the well, is derived by virtue of a change in a well-condition as the piston travels toward the end of one of itsstrokes and is effectively prevented from =operating the piston until it reaches the end'of a stroke whereby the piston cannot be prematurely reversed in-its direction of travel even though an'excess of force ispotentially available to do so.

Another general object is to provide a Well' system and free piston for use therein which does not require an artificial variation in a well condition at the well head to effect a reversal of the pistons direction of travel.

Another object of the invention is to provide such a system and piston wherein a mechanism for positively operating=the piston to cause or permit it to reverse its direction of travel at the end of one of its strokes is contained within the piston itself and only very simplewell head or subsurface equipment need be employedto cooperate with such mechanism in positively determining the terminus of one of the strokes of the piston.

Another object is to provide a well system and a free piston for usetherein in which the power developed by motor means as a result of the change in well condition encountered by the piston as it moves through a well conduit is effectively restrained from operating the piston permit it to reverse its direction of travel until the piston encounters a means situated at a predetermined level in the conduit whereupon the motor means is released to deliver power to operate the piston and permit it to reverse its direction of travel only upon reaching said predetermined level despite an excessive change in said well condition.

Another object is to provide a well system and a free piston for use in a well conduit of such system wherein means restraining actuation of certain piston parts is itself prevented by the well conduit from releasing such actuatable parts whereby the direction of travel of. the piston cannot be reversed while the piston is moving along the conduit but only after it encounters a particular section of the conduit whereby location of such particular section locates the terminus of one of the pistons strokes.

Another-object is to provide a well system and a free piston for use in such system wherein energy for operation of the piston to permit it to reverse its direction of J movement is accumulated in the piston as it moves along the conduit and wherein means are provided for releasing such energy responsive to the piston encountering a means carried by the conduit whereby the ends of the piston strokes are determinable irrespective of the excess of energy stored or the rate of storage thereof.

Another object is to provide a well system and a free piston for use therein wherein force for actuation of parts of the free piston to permit it to reverse its direction of travel from one of its strokes is released by a latch or trigger means carried by the piston and responsive to the pistonarriving at a predetermined level in the well so that the piston always arrives at such level irrespective of the excess of force applied to actuate the parts prior to arrival of the piston at such level and wherein such force for such actuation can be released by a variety of mechanisms including but not limited to those actuated responsive to the piston encountering a stop in the well, or a predetermined temperature, or a predetermined pressure whereby operation of the piston can be made flexible and adaptable to many well conditions.

Another object is to provide a free piston wherein a motor means exerting a force to operate the free piston, which force is of a magnitude varying with a change in a well condition along the path of travel of the piston, is positively prevented from operating the piston while it moves in one direction by a latch held in latching position by a conduit through which the piston moves and movable outwardly of the piston to unlatching position upon encountering an enlargement in the conduit, the latch also preventing operation of the piston by such force during movement of the piston in an opposite direction until the force becomes of a predetermined magnitude whereupon the force is released without moving the latch outwardly whereby one terminus of the stroke of the piston is made dependent upon a well condition and the other upon a physical condition of the conduit.

Another object is to provide a free piston which includes a temperature responsive means for actuating a latching mechanism so as to release a force applying means to actuate the piston and thereby terminate one of its strokes wherein the temperature responsive means only releases the accumulation of force which is derived from another source.

Another object is to provide a free piston which includes a latching mechanism for holding a force applying means to prevent it from actuating the piston, the latching mechanism including a trigger means adapted to strike a stop in a well conduit to release the latching mechanism and thereby permit the force applying means to actuate the piston.

Another object is to provide a latching mechanism adapted to prevent relative movement between two motor driven parts of a well apparatus despite force applied to cause such movement, the latching means being held in latching position by a well conduit as the apparatus is moved therethrough and being releasable only upon encountering a particular configuration of the conduit.

Another object of the invention is to provide a free piston in which a resilient means and a packer actuating part are arranged for movement together in expanding or collapsing a packer whereby movement of such part in one direction to actuate the packer does not involve opposition of the resilient means and movement in the other direction transmits force to the packer only through the resilient means.

Other objects, advantages and features of this invention will be apparent to one skilled in the art upon the consideration of the written specification, the appended claims and the attached drawings wherein:

Fig. 1 is a schematic illustration of the well system of this invention showing a piston in a lubricator at the well head and, in dashed outline, at the bottom of its stroke ready to start its up-stroke;

Fig. 2 is a detailed view of a manual catcher for holding the free piston in the lubricator when desired;

Figs. 3A, 3B and 3C are views, partially in section and partially in elevation, illustrating a preferred embodiment of a free piston constructed in accordance with this invention, it being understood that the views are lower continuations one of the other in the order above named;

Fig. 4 is an isometric view showing the major portion of the apparatus sectioned in Fig. 3B;

Figs. 5, 6 and 7 are cross-sectional views taken along the lines 5-5, 6-6 and 77 of Fig. 313;

Fig. 8 is another isometric view illustrating one part of the apparatus of Fig. 3B which part is shown to be inverted from its Fig. 3B position for the sake of clarity;

Fig. 9 illustrates an alternative embodiment which can be substituted for the structure of Fig. 33C to be combined with that of Figs. 3A and 3B;

Fig. 10 is a view on a line 1010 of Fig. 9;

Figs. 11, 12A and 12B illustrate an alternative embodiment of free piston constructed in accordance with this invention, it being understood that Fig. 11 is a view taken 90 from that of Fig. 12A with certain portions broken away to better illustrate the arrangement of the parts;

Figs. 13 and 14 are isometric views of certain parts shown in Fig. 12A;

Figs. 15 and 16 show still another embodiment of the free piston of this invention and incorporating a timing mechanism for determining actuation of the free piston;

Fig. 17 is a vertical section taken on the line 17--17 of Fig. 15; and

Figs. 18A and 18B illustrate yet another embodiment of a free piston and one in which temperature responsive motor means are provided for actuating the free piston.

Like characters of reference are used throughout the several views to designate like parts.

In Fig. 1, there is shown an exemplary well system of this invention in which a free piston 15 is reciprocated in a tubing 16 disposed in a well which can be cased as at 17. For the embodiment of the free piston shown in Figs. 3A through 3C, a pressure responsive motor acts under the influence of well pressure at the lower end of the downstroke of the free piston to cause it' to form an impermeable plug in the tubing; that is, to prevent the flow of fluid in the tubing past the piston. Flow of fluid up the tubing will then cause the piston to rise of enlarged cross-sectional area.

therein and such flow can be either natural or induced as by injection of gas into the casing through a conduit 18 and thence through a gas lift control valve 19. The tubing-casing annulus can be packed as at 20, if desired, to prevent the application of lifting gas pressure to the formation. At any rate, as thepiston rises up the tubing, it forces fluid thereabove upwardly along the tubing to be discharged through ports 21 in lubricator 22 and finally out through a flow line 23. After the piston has arrived at the upper end of a stroke as shown in the upper portion of Fig. 1, a mechanism is operated permitting the free piston to be actuated so thatfluid can bypass the same in the tubing. Thereupon, the free piston is free to fall by gravity down through the tubing until it strikes a stop 24 which permits or causes the free piston to again form an impermeable plug in the tubing. The free piston can thus act as an aid in improving the gas lifting efliciency of a well, as a paraffin scraper, or for other purposes.

It will be noted that lubricator 22 is provided with a portion 25, which can be considered a part of the tubing, The function of this enlargement is to permit a triggering mechanism carried by' the free piston to release a motor means or energy source so that the latter can operate the free piston to permit fluid to by-pass the same. This will be discussed in greater detail below.

If desired, a manual catcher 26 can be provided as a part of the lubricator to catch the free piston when it trated in Fig. 2.

28a pivoted about a pin 29so thatian upper-end 30 of V the dog can be biased outwardly by spring 31 to engage falling back down.into thewellin the event that it is desired to stop. the operation iofthehfreef piston orto remove it from the well. WIn-this connection,.a.master valve 27 can also be'provided to closeinthe well and permit the free piston to be removed from the lubricator. Further, ashock absorber-designated generally by the numeral 28, can be provided as a part of-the lubricator to cushion the impact of the free piston-as it; arrives at the surface of the -well. 1 I

' The details of the catchingmechanism 26 are illus- .In this .figure, there is shown a dog a shoulder 32 on the free piston A rotatable pin 33 having a cam head 34 can be provided to engage an ear 35 on the dog to hold the dog in retracted position when it is desired that the free piston should-tall down into the well. However, when pin-33 is rotated to the position shown in Fig. 2, spring31 urgesdog 28ato pivot so that part 30 thereof is situated: in the path of the free piston. Then as the free piston moves upward-dog 28a will ride over the outer surface thereof to jump under a shoulder 32 and prevent the free piston from falling back down the well.

In one preferred embodiment of the freepiston of this invention, as shown in Figs. 3A through 3C, it is provided with a motor means 36, here shown to-be of the pressure responsive type, which, underthe influence of a changing well condition, provides the necessary-force for operating the free piston. .Thus, :asv the piston drops down the tubing to be exposed to increasing well pressures, the pressure responsive motormeans exerts a force tending to expand packer 37 and close valve means 38 so that the piston will become a substantially impermeable plug in thetubing. However,'such'force is prevented from being applied to achieve these functions byalatching mechanism 39 which isreleased by striking against stop 24. Thereafter, the piston forms-animpermeable plug and can rise up the tubing under influenceof fluid flowing throughthe tubing. At someinterval before'thc piston is to begin its downward-stroke,"the-motormeans will be exposed to adecreasedwell-pressure so that it tends to apply force to contract packer 37 and open valve 38. However, it is prevented from'doing this by another latching mechanism 40 which doesnot-release the force until enlargement 25 in the lubricator is encounteredby the free piston. Then upon the forceb'eing released, the motor means contracts the -paoker and -opens the, valve so that the free piston can fall-back. downqthe tubing. In this manner, the lower terminus ofathe free piston stroke is determined by a physical -stopcarried by the tubing and its upper terminus is determined by an enlargement also carried by the tubing By-proper construction of the motor means, the piston is given a snap action in its'operation to reverse its stroke, premature actuation of the free piston is prevented so thata it eannopu-ever'se its stroke even though the pressurertowhich it is1exposed may be more than suflicienttodevelop the .-forc'e; required for doing so, and artificial -variation -in-well pressure is not required in assuring the piston will-function{:satisfactorily.. Y I 7 Now referring to the details .of-construction shown in Figs. 3A through 3C, the motor means of the free piston is illustrated as comprising a-piston 4l- -having a sliding seal, as by O-rings 42 and- 43 with an inner-bore 44 of pressure dome housing'45. The pressure dome 45a can be charged witha resilient-fluid ('eitlierdgas alone or a mixture of gas and liquid) through achargingport 46 controlled by a chargingrvalye 47. and-sealed-by plug 48. In this manner, the pressure' dome can'becharged'to a predetermined pressure sothat the-charged fiuid urges piston 41 outwardly to increased thevolume of closed chamber 45a. I Toaid in thisefunction, a spring-49 can be disposed between .piston 41; and. theupper-end :of

:the dome housing. The preferred pressure to whi chthe pressure dome" is charged and the. preferred strength of spring 49 will be discussed in detail below after certain other portions of the tool have been described in detail.

' Pressure dome housing 45 is connected to a fitting-50 which extendstor connection with an outer sleeve housing 51 while piston 41 is connected via a stem 52 to an inner sleeve 53. Sleeves 51 and 53 are provided with ports 54 and 55 which constitute the valve means 38. These ports are so arranged-that movement of pistons between its V innermost and outermost positions in the pressure dome respectively causes the ports to be out of and in-regis'ter ,toacontrol fluid flow from one end of the piston to the othertoby-passpacker 37 via lower ports '56 and 57s and inner passage 58.

As indicated above, pack-c1 37 is to be expanded to form a sliding seal with the walls of the tubing to prevent iluid from by-passing the free piston on its up-stroke and then contracted so as to permit such fluid to by-pass during the downstroke of the pistonand, of greater importance, .also to reduce the frictional resistance .to the fallv'of the free piston. While the packer can be made in a number of differentmanners, it is preferablycomprised of resilient sleeve havingone end fixed to outer housingsleeve 51 and the other connected to the inner sleeve 53 so that relative longitudinal movement between .thesesleeves causes the packer to be contracted and expanded radially. Thus, the upper end of the packer can be connected tothe outer sleeve as by means of a' metal cap ring 59 bonded toone end of the packer and held to outer sleeve 51 as by locking pins 60. The latter can be maintainedin place by a keeper ring 61 which is prevented from being displaced by a snap ring 62. The lower end of the resilient packer likewise is provided with a metal cap ring 63 bonded to the packer and providing an inner shoulder.6d=engageable with a part 65 extending from the inner sleeve through a slot 66 in the outer sleeve. In

this manner, movement of inner sleeve downwardly relative to outer sleeve 51 causes part to engage lower cap ring 63 and contract the packer. In order to expand the packer upon upward movement of inner sleeve 53 relative to the outer sleeve,. the inner sleeve is provided with a cross pin 68 extending through slot 69 in the outer sleeve to connect spring retainer ring 70 and spring '71 to the inner sleeve. The retainer ring is provided with a slot extending thereinto from its lower edge which engages the outer ends of cross pin 68 so the retainer ring can be lifted upwardly and pin 68 moved into or out of position. Upon lowering the ring, the pin will beheld in place thereby. In this manner,- as inner sleeve 53 and part 65 move upwardlyso that packer 37 can expand,

pin 68 and ring 70-will likewise move upwardly which tendsto compress spring 71 thereby urging the I lower end of the packer upwardly to expand the packer. Upon downward movementof the inner sleeve, the pin and ring move with the inner sleeve topermit the lower endof the packer to move downwardly also. One advantage of'this construction is that as the inner sleeve moves downwardly to contract packer 37, the stress exerted by spring 71 on the packer is relieved so that it is not necessary to com- "press the spring during contraction of the packen' In to provide additional force to compress the packerexpander spring. In such a situation, the packer when expanded will beheld in expanded position not only by its own natural resiliency but also by the force exerted-by spring 71 while sleeve 53 is in its upper positionrThen as the free piston moves upwardly through the tubingand encounters slight variations in the crossse'c'tionthereof,

the packer= is free to expand and contractinwardlywand 7 outwardly against the resilient force of spring 71 to maintain a sliding seal with the tubing,

In orderto prevent flow through the tool when valve means 38 is closed and packer 37 expanded, a sliding seal in the form of a piston 72 and 'O-ring 73 is carried by stem 52 to reciprocate in a bore 74 within the upper part of outer sleeve 51.

From the foregoing, it will be seen that pistons 72 and 41 must be maintained in suitable axial alignment with their respective bores and yet inner sleeve 53 should be permitted to slide relatively freely within the outer sleeve. To avoid a difficult aligning problem, an articulated connection is provided between stem 52 and sleeve 53. Thus, the lower end of stem 52 can be cut to form a T-head 75 adapted to extend into ports 55 of the inner sleeve thereby giving the connection some lateral flea'i bility. To permit assembly of the tool, the upper end of the inner sleeve is split as at 76 to permit the upper end to be spread apart and slid over T-head '75 after which it springs back into its normal position as shown in Fig. 3B. After the articulated connection is thus assembled, the

- entire inner assembly including stem 52 and sleeve 53 can be slid into proper position within outer sleeve 51.

As thus far described,- it will be seen that the free piston comprises a body means including portions movable relative to each other to permit and restrict flow from one end of the free piston to'the other. While both packer 37 and valve means 38 are shown as a flow control means comprising a part of'the relatively movable portions, it is possible to close the by-pass on the inside of the packer and depend solely on flow between the contracted packer and tubing to permit the free piston to fall down the tubing. Alternatively, the packer could be arranged to remain in contact with the tubing and the valve means only employed to control the flow between the ends of the piston. However, it is preferred to employ both the contractible packer and the valve means in the interest of increased etficiency of performance.

As before mentioned, latching or triggering means 49 is provided to prevent opening of valve means 38 and the contraction of packer 37 until the piston arrives at enlargement 25 even though the motor means has previously to such arrival developed sufficient force to so actuate the valve means and packer. In the form shown in Figs. 3A-3C, there is provided what may be termed a one-way top trigger forreleasing the motor means to actuate the piston upon arrival of the piston at the lubricator and a contact bottom trigger adapted to also release the motor means when the piston encounters a stop in the well. Thus, the piston is provided with'levers 5 or triggers 80 pivoted by pins ditto fitting 5i) so thatthc lower ends 82 of the levers can swing from a retracted position as shown in Fig. 3B to an extended position as shown diagrammatically in Fig. l. The levers are urged to retracted position by springs -83 andhave a releasable connection with stem 52 such that downward movement of the stem under the influence of the motor means is prevented until the levers move to extended position.

Thus as a part of such connection, latch fingers 8d are pivoted by pins 85 to the levers and are'urged from their unlatched position as shown in Fig. 313 to a latching position by springs 86. Stop parts, in the form of opposing shoulders 87 and 88 respectively carried by the latch fingers and levers can be provided to limit movement of the latchfingers toward latching position. Stem 52 of the motor means is providedw ith abutment surfaces which are here shown as being supplied by a pair of antifriction' rollers 85* rotatably carried by the stem on shafts 90. The lower surfaces of the rollers are so positioned on the stem that when piston at is in its uppermost position in dome 45a, the rollers will be positioned above upper ends 91 of the latch fingers whereby springs 86 can pivot the latch fingers inwardly until stop parts 87 and 88 are in abutment. tion, downward movement of stem 52 will be limited as With the mechanism in such posilong as neither the latch fingers nor the levers pivot outwardly. ,Outward pivoting of the latch fingers about pins 85 is prevented by arranging the fingers so that the force-tending to pivot them inwardly, when the fingers are in roller engaging position, is greater than the force urging them to pivot outwardly. Thus, the axes of pivot pins 85 areolfset outwardly of the engagement between the rollers and the latch fingers, and each of ends 91 of the latch fingers is disposed at an angle with the longitudinal axis of the stem, such that when the latch fingers are in engagementwith the rollers, the sum of the turn ing moments of (1) the resultant of the axial force of the stem applied to the latch fingers to pivot them inwardly and (2) the inwardly pivoting force of springs 86 fingers 84 engaging the underside of rollers 89.

is greater than the turning moment of the resultant of the axial force of the stem applied to the latch fingers to pivot them outwardly. Stated in another manner, when the latch fingers are in latching position, they contact the rollers inwardly'of the dead center contact position thereof which dead center position is the pivotal position of the latch fingers where the pivoting movement (including springs 86) urging them inwardly equals the pivoting moment urging them outwardly. Accordingly, downward thrust on the latch fingers by stem 52 prevents them from flying outwardly to release the stem. However, the latch fingers have only limited inward pivotal movement due to stop parts 87 and 88 being brought into abutment so that the net efiect of force applied by the stem to the latch fingers is to urge levers 32 outwardly to extended position. It will be noted that the lever pivot pins 81 are situated such that a plane through the axes of pins 81 and 85 of each lever lies laterally outwardly of the engagement of the rollers and latch fingers so that the force transmitted by the latch fingers to the levers urges them to pivot outwardly to extended position. In a preferred embodiment, both pins 33. and are offset laterally outwardly of the locus of engagement between the latch fingersand the rollers so that the distance between the axes of each of the pins and the central longitudinal axis of the stem 52 is greater than that between such longitudinal axis and the point of contact be tween rollers 89 and the upper ends 91 of the latch fingers. In the illustrated embodiment, this diiference in offset and the'angular disposition of ends 91 is such that an angle a of the order of 20 exists between (1) a radius r" drawn from the axis of a shaft S t normal to a line I tangent to the rollers at their contact with the upper ends of the latch fingers and (2) a line 1' drawn between the axis of 'a corresponding pin 81 to such contact. With this construction, it will be seen that though the motor means 36 exerts a substantial force tending to move stem 52 in a direction to open valve 33 and contract packer 37, such force will be resisted by latch This force results only in urging of ends 82 of the levers outwardly into engagement with the inner walls of the tubing string. Of course, the parts are so dimensioned relative to the tubing that even when the lower ends 82 are in sliding contact with the tubing, the upper ends 91 of the latch fingers are still on the inside of dead center" of the rollers so that downward force exerted thereon will not cause the latch fingers to pivot their upper ends outwardly about pivot pins 85. However, upon arrival of the free piston at enlargement 2,5 as shown in T Fig. 1, room is provided for the lower ends of the lever i has positioned the inner sleeve in ...,s,sss,oos

as increase and tend to force it into the pressure dome so 1 as to close valve 38 and permit the packer to expand.

In order to prevent this untilthe free piston has arrived at a predetermined level in the well, a bottom latch mechanism 39 is provided as shown in Fig. 3C. This mechanism can comprise a lower dogcarrier 2. connected to inner sleeve 53 as by pin as carrying a pair of latching dogs 93. These dogs have shoulders 94 adapted to engage corresponding shoulders 5 55 on iower trigger housing fitting 96 to prevent upward movement of the inner sleeve relative to the outer one until the free piston strikes a stop in a well. The stop can, of course, be any suitable obstruction carried by the tubing, either permanently or wire line removable.

To maintain the dogs in latching position and then to permit them to swingtounlatched position upon the piston striking the stop, a trigger means or plunger 97' is provided having an enlarged portion 98 adapted to be moved between rollers 99 on the latching dogs to hold them in latching position. A part of the trigger extends as at 100 for contact with the stop in the well to move enlarged portions98 upwardly so as to permit the latching latching position. The trigger is, of course, held in and urged to latching position by a spring 101. This spring should be strong enough to force enlarged portion 98 between the rollers d9 of the latching dogs to move them outwardly into their Fig. 3C position after the motor means its downward position. This occurs at the top of the well, of course. Then as the piston falls down the well, the well pressure can increase on the motor means so that it urges inner sleeve 53 upwardly relative to the outer sleeve but such-movement is prevented by the latching dogs 93 being held in latching position by the trigger.

However, upon the free piston striking the stop in the well, the trigger, including enlarged portion 98, is moved upwardly to permit the dogs to swing inwardly to unlatched position under the influence of forceapplied by the motor meansacting through the upwardly and inwardly inclined surfaces of shoulders 94 and 95. The inner sleeve can then move upwardly relative'to outer sleeve to expand the packer and close the valve.

Pressure dome 45a should be charged at a pressure such that the sum of the forces exerted by the charge fluid and spring 49 will exceed the counter force exerted on piston 41 by the maximum well head pressure sufficiently to cause the operation of the various mechanisms driven thereby. On the other hand, such sum of forces should be less than the force exerted on the piston by well pressure encountered at the lower end of the free pistons stroke sufiiciently to cause operation of the free piston. By this arrangement, the well pressure gradient always can cause or permit an excess of force to be developed at the ends of the pistons strokes to cause the desired operation of the latching mechanisms, packer, valve means and the like without premature operation thereof. Further, the types of latching mechanisms just described permit the dome to be charged at a pressure substantially greater than the maximum well head pressure and yet the piston will not be actuated to begin its return stroke until it arrives at the surface of the well; That is, the piston cannot be actuated, no matter how great the excess of force exerted by the motor means, until it arrives at enlargement 25 in the lubricator. On the other hand, the free piston must always fall until it'strikes stop 24 before it can begin its ascent no matter how much the well pressure excess be in the vicinity of the'stop. This means then that the magnitude of thecharge of the resilient fluid or the strength of spring 49 is not critical in the sense that it would determine the length'of stroke of the piston or the termini thereof.

In a preferredembodiment,the'space'betweeri Q-rings dogs to move inwardly and thereby into un- 42 and 43 on piston 41 is connected via bores 102 and illlZato a one-way check valve 103. .The check valve can comprise an insert seat 1 34 and a valve member 105 urged against the seat by a spring 106. Spring 166 is of such strength relative to the cross-sectional area of the seat between valve member 165 and insert seat 104 that the pressure in bores lld2-iti2a will not exceed the pressure outside the free piston by more than a predetermined value. This diiferential can be made quite small, as, for example, a few pounds per square inch, e. g. five, so that even if O-ring 43 should tend to leak so as to increase the pressure in bores ELM-402a, the differential will always return to its predetermined value each time the free piston comes up into the relatively low ambient pressure at the well head. O-Iing 43 may possibly leak when it is exposed to the high pressure at the lower end of the free pistons stroke thereby increasing the pressure in bores 1fl2-102a. However, while the piston is at the upper end of its stroke and hence exposed to the lower well head pressure, the check valve will open and bleed down the space between O-rings 42 and 43 to a value determined by the strength of spring 106. In this manner, a very low difference can be recurrently re-established across O-ring 43 so as to minimize leakage thereacross even though O-ring 43 should leak. It should be noted that the object of this construction is to preserve the pre-established pressure in dome 4511 by minimizing leakage past O-ring 42. This object is achieved by arranging that the pressure in bores 102102a will be maintained different from that in dome 45a, the difference being self-preserved. This results in O-ring 4-2 being pressed against only one side of its groove in piston 41 and is prevented from rolling when the piston moves. In the arrangement of this tool, the O-rings move only while the free piston is at the upper and lower termini of its stroke. At the upper terminus, any excess pressure in bores Tim- 102a is relieved before the O-ring to leak is greatest.

42 is moved and, hence, only a preselected differential can exist across it during its movement when the tendency On the other hand, when the free piston is approaching the lower end of its stroke, the low differential remains across O-ring 42 since the O-r-ing 43 is not moving and hence has a minimum tendency to leak even though the diiferential across it is high. immediately after {i -ring been .ioved under the high differential which might cause it to leak, the free piston starts its upward journey so that the time an increased ditlerential can be applied across O-ring 42 is during the upward journey of the free piston. Although leakageacross O-rings 42 and 43 will usually be very small for each cycle of the free pistons operation, continuous operation of the free piston could, it will be understood, cause excess pressure to accumulate between the O-rings and create ditficulties if means for continuous correction were not provided.

It is very desirable that the total volume of bores 162- 102a be quite small. When the freepiston is originally inserted into the well, the pressure in these bores will be atmospheric. Then with the volume of the bores being small, only a very small amount of fluid need leak into the bores to bring them up to design conditions. Thus, the design conditions can bequickly achieved.

The free piston as thus far described in detail is provided with a bottom stop release means adapted to be actuated upon contact of the free piston with an abutment carried by the tubing. in Fig. 9 is shown an alternative arrangement adapted to be substituted for that of Fig. 3C and involves a temperature responsive means which re leases the motor means to close valve 38 and expand packer 3'7- whenever the free piston encounters fluid in the well of predetermined temperature. Thus, many wells have a pronounced temperature gradient and it may be desirable that the free piston. continue its downward travel. only until it encounters fluid of a temperature of predetermined magnitude. For example, some well fiuids will not-depositpar'amn on the tubing until they 11 have been cooled to a certain temperature and by setting the free piston to start its upwardjourney at a point where the well fluids are still above the initial paraffin deposition temperature, the free piston can be used as a paraffin scraper without causing it to traverse the entire length of tubing.

Referring now to Figs. 9 and 10, part 65 carried by inner tube 53 is provided with a crosshead lltl'from which depends a stem 111. The lower end of the stem has a latching head 112 engageable by a trigger or latching bar 113 which is pivoted for movement about a pin 114. The free or swinging end of the latching bar is contacted and moved by a temperature sensitive means, preferably a bi-rnetallic strip 115 which has its other end fixed eccentrically to an adjusting disc 116 so that upon turning of the disc, the bi-metallic strip will be wound or unwound to adjust the mechanism to different temperatures at which the strip will pull latching bar 113 out of engagement with latch head 112. The latching bar is urged to latching position by a spring 117.

It will be noted that in this instance spring 71 abuts housing 113 which is carried by outer sleeve 51. As a result, when inner sleeve 53 moves to contract packer 37, it will necessarily have to compress spring '71, thereby adding to the force required to position the parts of the free piston for movement in its return stroke down the hole. While this structure can be employed, it is here illustrated primarily to show the advantage of the structure of Fig. 3C which does not require compression of spring '71 in contracting of the packer. Accordingly, it

is preferred that the spring arrangement of Fig. 3C be combined with the temperature sensitive means of Fig. 9 to replace the spring arrangement illustrated in such figure.

rom the foregoing, it will be seen that the free piston still must move upwardly through the tubing until enlargement in the lubricator is encountered so that levers 89 can swing outwardly to release latch fingers 84 and permit the stem 52 and inner sleeve 53 to move downwardly relative to the outer sleeve. Upon having so moved, latch head 112 will engage latch bar 113 under the influence of spring 117 independently of himetallic element 115. Then as the piston falls downwardly through the tubing, well fluids of increasing temperatures will. flow inwardly through ports 119 into housing 118 and thence outwardly of the housing through the clearance between stern 111 and the upper end of the housing. When the fluids have heated bi-metallic strip 1.15 sufiiciently, its pin 115a will engage latch bar 113 and. swing it to unlatched position thereby permitting release or": stem 111 so that motor means 36 can move valve means 38 to closed position and permit packer 37 to expand. One advantage of the arrangement shown in Fig. 9 is that the movement and force which must be generated responsive to a change in temperature need be only quite small in that it only need be great enough to move latch bar 113 out of engagement with the latching head. it is not necessary that such movement be sufficient in magnitude or force to either open or close valve means 38 or to contact or expand packer 37. Accordingly, the mechanism can be made very compact and only a relatively weak temperature sensitive mechanism provided.

In Figs. 11 to 14, there is illustrated a free piston similar in many respects to that of Figs. 3A-3C, except that triggering or actuation of the free piston to close the valve means and expand the packer at the bottom of the stroke is made responsive to the motor means exerting a force of predetermined magnitude on the triggering mechanism. Stated in another way, the lower end of the free pistons stroke is determined by a well pressure of a predetermined high value. As shown in Fig. 12A, stem 52 is provided with an abutment having opposing surfaces 120 and 121 adapted to respectively engage upper ends 91 and opposing surfaces 122 on latch fingers 84a.

12 Here again, a pair of trigger levers are pivoted about pivots 81 so that the lower ends 82 can swing between retracted and extended positions. In this instance, each latch finger 84a and lever 80 is urged into latching position by a. single spring 123, the movement of latch finger 8dr; toward latching position being limited by abutment of stop parts 87 and 83. Thus, with the parts arranged as shown in Fig. 12A, a force exerted by the motor means tending to move stem 52 downwardly will be resisted by surraees 129 on the stem. As soon as the free piston arrives at enlargement 25 in the lubricator, ends 32 of the levers are free to fly outwardly and thereby release the latch fingers from engagement with the stem. They, of course, are urged to this outward position by the force exerted by the motor means. On the other hand, when stern 52 has been moved downwardly by the motor means upon release of the latch fingers by levers 80, lower opposing surfaces 122 on the latch fingers will engage upper surfaces 121 on the stern abutment and force applied thereafter tending to move the stern upwardly will be resisted by this engagement. As the free piston moves down the well and Well pressure becomes greater on the motor means, the upward force exerted on the stem will likewise increase and eventually will become great enough to cause latch fingers 84a to pivot outwardly about pivots 35, and against springs 123, to disengage the latch fingers from the stem. The motor means can then permit or cause the packer to expand and also close valve 38.

To cause the above described actuation of the latch fingers 84a and levers 80 by the pressure responsive motor means, upper ends 91 and pivot pins 81 and 35 are arranged as described with respect to the corresponding parts in Fig. 313 so that the'inward turning moment on the latch fingers exceeds the outward turning moment thereon. However, in Fig. 12A, the upper ends 91 are shown to be in a plane normal to the longitudinal axis of stem 52 so that there does not exist any outward turning moment. This is not essential but it does illustrate another arrangement. The lower abutment surface 122 on the latch fingers and upper surface 120 on the stem are also shown to lie in a plane normal to the longitudinal axis of the stem. Accordingly, the only turning moment on the latch fingers when the surfaces 121 and 122 are. in abutment is outward and when the upward axial thrust to the stem becomes great enough to cause the outward moment to overcome springs 123, the latch fingers will fly outwardly to release the stem for actuation of the free piston and instigate its upward stroke. Thus the latch fingers resiliently lock the stem in its down position and are releasable responsive to a well pressure of predetermined magnitude being exerted on the motor means, all with-out moving levers 80 to extended position. Of course, the laterally outwardly offset position of pins relative to the engagement between surfaces 121 and 122 pedmits this to occur. Further, the angular disposition of surfaces and 122 can be changed in order to change the axial thrust required to swing the latch fingers outwardly thereby changing the well pressure necessary to actuate the free piston. Changing the strength of springs 123 will also result in a similar effect. In any event, as soon as the stem moves upwardly sufficiently. springs 123 will move the latch fingers back in under surface 120 to prevent downward movement of the stem as the free piston rises up the tubing and until it arrives at enlargement 25 in the lubricator.

As indicated above, both the axes of pivot pins 35 and 31 are disposed laterally outwardly from the points of contact between the latch fingers and the stern. In a typical instance, a suitable ofiset for pin 85 is such that an angle of the order of 20 is bounded by (l) a line drawn from surface 121 (with the latch finger surface 122 engaging surface 121) through the axis of pivot pin 85 and (2) the longitudinal axis of the stem. Similarly, a suitable offset for pin 81 is such that an angle of 20 t st o the upper ends of latch fingers 34a with lower than enough force for doing so.

. aseaooe is bounded-by (1) a line drawn from surface 120 (with .the latch finger end 91 engaging this surface 120) and the axis of pivot pin 81 and'(2) the longitudinal axis of the stern.

It will be understood'that charge chamber 45a of Fig.

12A is not shown in its entirety and that the upper end thereof'canterminate in a charging valve, a plug 48 and a fishing neck, all asshown in Fig. 3A. Also, instead of the pistontype of pressure responsive means as shown I in Fig; 313, a bellows type is illustrated as including a bellows 124 fixedly connected at one end to the pressure dome housing 45 and at the other. to an extension 5212 of stem 52. An inner guide 125 can be carried by the dome housing to aid in maintaining the bellows in proper axial alignment. Also, damping means can beprovided to slow down the operation of the motor means. Thus,

' the stem extension 52b can be provided with different isizcdpistons 126 and 127, each having a sliding seal with a cylindrical portion of the dome housing 45. The effective diameter of piston 126 is made equal to the effective diameter or" bellows 124 so that a suitable liquid can be disposed in spaces 128 and 129 withoutcausing the'mechanism to fluid-lock. These spaces are interconnected across piston 1'27'by arestriction 13tlso that the arrangement acts as a' dampener to prevent excessively rapid movement of the stem.

The bellows arrangement of Fig. 12A can be substi- 'tuted for the piston type arrangement of Fig. 3B and vice been provided for releasably retaining pins 81 in position and also for locking thescrewed connectionbetween dome housing and fitting 50. This arrangement involves a holding member 131 having an upper end 132 extendingthrough a slot in fitting into a slot in housing '45 and the lower end into a snap ring retainer 133. A snap ring 134 in a groove in the retainer serves tolock the lower end of member 131 in place. The member, of course, has portions thereof extending to lie over the heads of pins 81. A similar strip 135 extending downwards through a slot in fitting 5t locks the screwed connection between fitting 5t and outer sleeve 51. A different arrangement is shown in-Fig. 12A wherein plates 14% are pinned to stubs 141 carried by part 50 and by covering the ends of pins 81, lock the latter in place.

i From the foregoing, it will be seen that when a free piston constructed in accordance with the showing of Figs.

3A-3C is inserted in a well as shown in Fig. i, it can fall down the tubing while latches 93 prevent expansion of the packer and closing of valve means 38 even though the well pressure exerted on the piston 41 provides a force more than suflicient to accomplish these functions.

Then upon the free piston striking a stop, latches 93 are released, the packer expanded and the valve means closed.

As the piston travels up the well, premature contraction of the packer and opening of the valve means will be prevented even though the well pressure on piston 41 decreases to an extent such that it would provide more Such force, of course, acts through latch fingers 84 to urge levers 80 outwardly but outward movement is limited by the levers sliding along the tubing. Accordingly, the packer cannot be contracted and the valve means opened until the free piston reaches the lubricator and enlargement 25. For the structure shown inFig. 9, the operation of the free piston will be the-same on its up-stroke but during the downstroke,

- the force developed by increasing well pressure on piston 41 is released only after the temperature of the well fluid has changed enough to cause the temperature responsive =n1eans to .unlatch stern 111 thereby freeing the motor means to expandthe packer and close the valve means.

For the arrangement of Figs. 11-1213, theoperation of the free piston on its up-stroke is still the same but on its downstroke, the packer cannot be expanded and the valve means opened until the force developed by the well fluid acting on the motor means is'sutlicient to pivot latch fingers 34a outwardly against springs 123. By the time this happens, the well pressure will be sufficient to pro vide'ample' or an excess of force for moving. the piston parts to expand the packer and close the valve means. .In this manner, the freepistou is madepressure responsive to terminate its downstroke and position responsive to terminate its Lip-stroke.

Referring now to Figs. 15 to l7,there is shown an embodiment of a free piston similar in manyrespects to that of Figs.- 3A -3C except that triggering of the free piston to cause it toclose the by-passvalve andto expand the packer at the lower end ofits stroke'is made responsive to the lapse of a predetermined time interval occurring after the' free piston leaves the well head. As shown in Figs. 15 and 17, stem 52 is provided with a pair of abutments 149 having surfaces 156 adapted 'to' respectively engage the upper ends 91 on latch fingers 84. Here again, a pair of trigger levers are pivoted about pivots 31 so that the lower ends 82'can swing between retracted and extended positions. Each latch finger 84 and lever 81) is urged to latching position by a single spring 123. Thus, with the parts arranged as shown in Figs. 15 and 17, a force exerted by the motor means'tending'to move stem 52 downwardly will be resisted by abutment of the. upper ends of latch fingers 34 with surfaces 150. As soon as the enlargement 25 in the lubricator. It will thus be seen that this latching mechanism is arranged and functions like that of Fig. 3B.

A modification of piston 41 is shown in Fig. 15. It is shown with only one O-ring 42 'and with a recuperating passage 152 communicating between pressure charge dome 45a and the end of piston 41 exposed to well pressure. Flow through this passage is controlled by a suitable check valve here illustrated as comprising an O-ring 153 urged by spring 154 to seat across an annulus communicating with the recuperating passage. With this arrangement, dome 45a can be charged so that the pressure therein is sufiicient that, with the assistance of the spring 49, the reloading of the free piston will take place as soon as levers 80 swing out into enlargement 25 in the lubricator. Spring 154 is made of such strength as to maintain the charge pressure in dome 45a at a predetermined value. Thus, should fluid leak into the dome past O-ring 42 while the free piston is at a lower level in the well, the increased pressure in dome 45a will cause O-ring 153 to move downwardly from seated position against the counter force of spring 154 until the dome bleeds back down to the predetermined pressure.

Timing means are provided for triggering actuation of the free piston at the end of a predetermined time interval after the free piston leaves the well head. Thus there is provided a timing piston 155 reciprocal in a cylinder 156 defined by, a depending portion carried by piston 41. The cylinder is filled with suitable hydraulic liquid and the timing piston is provided with .means permitting it to move rapidly in one direction but limiting its movement in the other to be at a much slower and predetermined rate. Thus as a part of these means, a one-way seal, such as lip seal 157, is disposed between the timing piston and cylinder 156 so that as piston 155 moves upwardly, an etfective seal is formed with the cylinder preventing flow of liquid past the seal'from one side of the piston to the other. However, when the piston moves downwardly in the cylinder, liquid on the lower side of the piston can rapidly flow past the lip seal to the upper side of the piston. To time the pistons upward movement, a small orifice or passageway 158 is provided communicating from one side of the timing piston to the other. The timing piston is moved upwardly by spring 159 extending between piston 41 and an upper end 160 of a piston rod 161 extending through a seal 162 in piston 41.

Releasable latch means are provided for holding the parts of the free piston in a position such that valve 38 is open and packer 37 contracted. These latch means are arranged for release by the timing mechanism, upon lapse of a predetermined time, to in turn release the motor means so that it can close valve 38 and expand packer 37. Thus the latch means can comprise a pair of latches 163 pivoted for swinging movement about pins 164 on stem 52. Each latch is provided with a shoulder 165 engageable with the corresponding shoulder 166 on fitting 511. These shoulders are arranged relative to each other such that when in engagement, valve 38 is in open position and packer 37 'is in contracted position.

Means are provided for holding the latches in latching position and for releasing'them for movement to unlatching position. Such means can include a sleeve 167 movable downwardly by spring 168 to lie between rollers 169 on the latches to hold the latter in latching position. The sleeve is movable upwardly from between the rollers to permit latches 163 to move inwardly to release position. A trigger is provided for so moving sleeve 167 responsive to predetermined movement of the timing mechanism. Thus the trigger can comprise a piston rod 170 extending from timing piston 155 and slidable through sleeve 167. The rod has a head 171 adapted to engage sleeve 167 and move it upwardly as the timing piston nears the end of its timing stroke. The piston rod 170, of course, has a sliding seal 172 with a partitioning member 173 which defines-one end of the cylinder in which the piston cperates.

With the foregoing arrangement and just as the free piston leaves the lubricator, the parts will be disposed as illustrated in Figs. 15-17. As the free piston falls down the tubing, spring 159 moves timing piston 155 upwardly at a rate determined by the size of orifice 158 and the strength of spring 159. During this movement, rod 171) moves through sleeve 167 without moving the latter. After the timing piston has been moved upwardly sufficiently, head 171 engages sleeve 167 and moves it from between the latches permitting them to move to unlatched position. At such time, the free piston is at a lower level in the well and the well pressure acts against piston 41 with enough force to move it upwardly upon release of latches 163 thereby closing the by-pass valve and expanding the packer. Upon upward movement of piston 41, stem 52 also moves upwardly to position surfaces 158 above latch finger ends 91. Also, as piston 41 moves upwardly, timing piston 155 is moved through its return stroke by virtue of head 16% abutting a timing rod 174. It will be noted that the timing piston is free to move downwardly even though latches 163 are in release position since rod 170 merely slides through sleeve 167. The latter, of course, is held in an upper position by virtue of latches 163 being held under its lower end by fitting 51).

Upon the free piston arriving at the well head, levers 8d fly outwardly to release latch fingers 84' and permit stem 52 and piston 4-1 to move downwardly. As a result of such downward movement, latches 163 are positioned to move outwardly into latching position whereupon spring 169 moves sleeve 167 between the rollers of the latches to hold the latter in latching position. The timing stroke of the timing piston then begins.

It will be noted that though the timing piston 155 is moved in its return stroke as soon as latch parts 163 are released, it does not begin its timing stroke until after the free piston arrives at the surface of the well, levers 81) move outwardly and piston 41 moves downwardly to permit the free piston to begin its downward descent.

Reference was made above to the fact that the motor means could be responsive to a temperature change encountered as the free piston moves upwardly and downwardly in the well tubing. In Figs. 18A and 18B is shown one embodiment of a free piston incorporating such a temperature responsive type of motor means. As indicated in Fig. 18A, the upper portion of this free piston is essentially like Figs. 3A and 3B and hence will not require further description. However, the valve arrangement is somewhat difierent in that flow through ports 54 and 56 is controlled by a valve piston having a seal such as Q-ring 181 thereon. The valve piston is movable in sleeve 51 between positions above and below ports 56. Thus, when valve piston 180 is positioned below these ports, fluid can flow around the lower portion of the free piston, in through ports 56, then upwardly through sleeve 51 and finally out through upper ports 54. Upon upward movement of valve piston 180, flow between ports 54 and 56 will, of course, be interrupted and the valve be in closed position. Such movement of the valve likewise results in movement of pin 68 to expand and contract the packer in the same manner as described with respect to Fig. 3C. However, here spring 71 is fastened to both the lower end of the packer and to ring 79 so that it acts in both tension and compression.

As shown in Fig. 18B, there is provided a motor means operable by a temperature change to actuate the free piston. Thus, liquid chamber fitting 182 is closed at its bottom end by a filling plug 183 and at its upper end by a pressure responsive member such as a hermetically sealed bellows 184. Chamber 185 is partially filled with a liquid having vapor pressure characteristics such that the force required for actuating the free piston will be developed at the temperatures existing at both the upper and lower terminii of the free pistons stroke. The magnitude of the force developed will, of course, depend not only upon the liquid chosen and the well temperatures encountered but also upon the effective area of the bellows and the pressure charge, if any, in pressure dome 45a. The variables can be fixed so that the required force is developed. The charge in dome 45a should be sutficiently greater than the vapor pressure of the liquid in chamber 185 at the well head temperature that the required force is developed to actuate the free piston to begin its downward movement. Similarly, the charge pressure must be sufliciently less than the vapor pressure at the lower terminus that the force required to actuate the free piston is again developed. The charge can thus be varied to determine the depth to which the free piston will fall. One satisfactory liquid is methyl alcohol but binary mixtures of liquids can be employed to yield a desired vapor pressure range. In any event, there will be a portion of the bellows remaining unfilled by the liquid which will be filled by vapor whose pressure will be a function of the well temperature. The volume of this cavity should be such that the vapor pressure will always be adequate to move the bellows through its intended movement once such movement begins.

The upper or free end of the bellows is directly connected mechanically with piston 41 by means of a center spindle 52a which is pinned by pin 68 to a connector 186 formed as a part of an extension of bellows head 187. The bellows head extension carries a pair of spring arms 188 terminating in rollers 189. These rollers, upon downward movement of the bellows head, engage an inclinded surface 190 to be moved inwardly into a slot 191 in the bellows head extension until they are positioned below shoulders 192. Thereupon, they are moved outwardly to engage these shoulders and limit upward movement of the bellows. head and'spindle 52a until a predetermined force has been applied by the motor means to cause such movement. .111 this manner, the by-pass valve is held in open position and the packer held contracted until the free piston is exposed to a temperature sufficiently high to develop the force required to spring arms 188 inwardly and thereby release rollers 189 from shoulders 192. Thereupon, the motor means ,actuates the free piston to close the by-pass valve and expand the packer.

It is preferred that the volume of charge chamber 45a be great enough that the axial movement of piston 41 does not appreciably change the charge pressure. The efiective cross-sectional areas of bellows 184-and piston 41 are preferably made equal so that the eifect of well pressure on the mechanism is canceled out.

In operation and with spindle 52a in its downmost position and the free piston falling down the well, well fluids enter through ports 56 andexit through ports 54, thereby by-passing packer 37. Spring 71 is during such time under suflicient tension to contract the packer to such an extent that it is smaller than the tubing bore. While the free piston is falling, rollers 189 are positioned below shoulders 192 to limit upward movement of spindle 52a. As the free piston falls, the liquid in chamber 185 is heated by the rising temperature of the well fluids and the vapor pressure of the liquid in ,the chamber increases. When the total vapor pressure has risen high enough to insure that an axial movement of spindle 52a and upper piston 41, once it has been started, will continue for a full stroke, the resistance of spring arms 188 and rollers 189 is overcome so that the latter move inwardly and release the spindle for upward-movement. As the spindle moves upwardly, pin.68 likewise moves up to apply force to compress spring 71 and thereby expand the packer. With thisarrangement, .it will be appreciated that as wear takes place on the outside of the packer and an increase in axial compression movement is needed to achieve the same final diameter, less spring thrust, owing to the reduction of wall thickness, will suffice to obtain it. Thus the spring rating is selected to obtain conditions in whichthe packer will continue to be expanded out to achieve a complete shut off despite a comparatively large amount of tolerable wear.

As the spindle 52a moves up and the packer expands, valve piston 180 moves above ports 56 to effectively close the by-pass passage through the free piston. Also, rollers 89 on stem 52 swing latch fingers 84- outwardly until the rollers lie above their upper ends. Thereaftendownward movement of stem 52 is prevented until the free piston arrives at the lubricator' as described with respect to Figs. 3A-3B. 1

It will also be seen that resiliency is necessary between the slow motion provided by the expanding or contracting fluid in chamber 185 and the rapid movement of the spindle 52a. In this embodiment, such resiliency is provided by the compressibility of the vapor in the bell lows 134 and the gas in pressure charge chamber 45a.

It will be appreciated, however, that the elimination of the vapor in the bellows and the substitution of spring means would provide a mechanical resiliency in place of the pneumatic resiliency herein described.

Various timing arrangements for use with free pistons are described and claimed in the above-identified copending application and it will be appreciated that these can be employed with the type of free piston herein described, i. e., one which is essentially self-contained in that it is powered for actuation by a change in a well condition, as well as with the surface reloaded type described in such copending application. Also, thetemperature responsive triggering mechanism, such as is shown in Figs. and 11 hereof, can beusedwithithe surface reloaded type of free. piston. 'Thesameis .true

of the bottom stop type of trigger illustrated in Fig. 3C.

From the foregoing it will be seen that this invention is one well adapted to attain all of the ends and objects hereinabove set for 51, together with other advantages which are obvious and which are inherent to the system and structure.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention having been described, what is claimed is:

1. In a well system, a well conduit; a free piston reciprocal in said conduit, said free piston including motor means and also including flow control means carried by the free piston and actuated by the motor means to alternately limit and permit flow of fluid past the free piston upon arrival of the same respectively at a lower and an upper level in the well; and means preventing the motor means from actuating the flow control means until the free piston arrives at one of said levels including a part carried by the free piston and movable laterally thereof between retracted and extended positions, a connection between said part and one of said motor and flow control means preventing and permitting actuation of the flow control means when the part is respectively in its retracted and extended positions; said conduithaving an enlarged portion into which said part can move to assume its extended position upon arrival ,of the free piston at said one level; said motor means urging the part to extended position as the free piston moves toward said one level and the part being held in retracted position by the well conduit as the free pistonpmoves toward and until it reaches said one level wherebyactuation of the flow control means is positively prevented until the free piston arrives at said one level irrespective of the magnitude [of the force applied theretoby .said

motor means.

2. The system of claim 1 wherein one said part is ,a lever pivotally connected to said piston for movement of a portion thereof between said retracted and extended positions and wherein said connection includesa latch finger pivoted to the lever and engaging said one of the .motormeans and flow control means to prevent actuation of the flow control means when the lever is in retracted position, the axis of the pivotal connection of the-lever with the tool being offset laterally of the locus'of engagement between the latch finger and said one 'of the motor and flow control. means so that force exerted by the motor means against the latch urges the lever to extended position.

3. The system of claim 1 wherein said motor means includes a pressure responsive means connected-to the flow control means and movable by pressure applied thereto to actuate the flow control means, a closed fluid chamber defined at least in part by said pressure re- .sponsive means, and a liquid partially filling said chamber and having vapor pressure characteristics such as to apply suflicientpressure against said pressure responsive means as to be able to move it when the liquid is at temperatures substantially those at said upper and lower levels.

-4. In a-well system wherein a conduit extends into a well, a free piston reciprocal in said conduit and having first and second relatively movable portions, means permitting flow offluid from one end of the piston tothe other responsive .to relative movement of the portions in a first direction and substantially preventing such and in said second direction when the piston is at a different level in the conduit, and detent means including parts respectively carried by said piston portions and mutually engageable to prevent said relative movement between said piston portions in one of said directions while the motor means is urging said piston portions in such direction, one of said parts being movable laterally outwardly of the piston to become disengaged with the other part to release said piston portions for said relative movement and being held against such outward movement while engaged with the other part by contact with said conduit during reciprocal movement of the piston, said conduit having an enlarged portion into which said one part can move to release said piston portions whereby movement of said piston portions in at least one direction is restrained until the piston arrives at said enlarged portion irrespective of the excess of force applied by said motor means.

5. A free piston adapted to reciprocate between upper and lower levels in a well conduit which comprises, in combination, piston body means having a first portion movable between two positions relative to a second portion to permit and restrict flow from one end of the piston to the other when the piston is disposed in a well conduit, motor means urging said first portion from one to the other of its positions responsive to a change in a well condition between said upper and lower levels, and detent means adapted to prevent movement of said first portion while the piston is moving in at least one direction hetween said upper and lower levels including a trigger part carried by one of said body portions and movable laterally of the piston between retracted and extended positions respectively within and without the outer circumference of the largest cross-sectional portion of the free piston so "that the well conduit holds the trigger part in retracted position while the piston is moving between said two levels, and a latch connection between said trigger part and the other of said portions preventing movement of said first portion from one to the other of its positions while said trigger part is in retracted position and releasing said first portion for movement to saidother position upon said trigger part moving to extended position.

6. The piston of claim wherein said latch connection includes a first element carried by said trigger part and engageable, when the trigger part is in said restracted position, with a second element carried by said other body portion to prevent movement of said first body portion from said one to said other position thereof and disengageable from said second element upon movement of the trigger part to said extended position, said elements permitting said first body portion to move to said one position thereof without movement of said trigger part to extended position. v

7. The piston of claim 6 wherein said elements are also engageable upon said first body portion tending to move from said other position toward said one position to prevent such movement until a predetermined force tending to cause such movement has been exerted by said motor means whereupon the elements become disengaged.

8. The piston of claim 5 wherein said trigger part comprises a lever pivoted on said one portion and said latch connection includes a latch finger carried by said lever, the latch finger engaging an abutment on said other body portion to prevent movement of said first body portion to said other position, the pivot of said lever being offset laterally of the engagement between the latch finger and abutment so that force exerted by the motor means urging the latch finger and abutment into engagement also urges the trigger lever to pivot from retracted to extended position.

9. The piston of claim 8 wherein said latch finger is also pivoted to said trigger lever laterally of the engagement between the latch finger and abutment to permit the abutment to swing the latch finger away therefrom so the abutment can move past the latch without movement of the lever to exended position when the first body porcombination, piston body means having a first portion movable between two positions relative to a second portion to permit and restrict flow from one end of the piston to the other when the piston is disposed in a well conduit, motor means urging said first portion from one to the other of its positions responsive to a change in a well condition between said upper and lower levels, and a releasable latching mechanism for holding the first body portion in one of its positions against force exerted thereon by the motor means including a trigger lever pivoted to the second portion for lateral movement of the trigger lever between retracted and extended positions respectively without and within the outer circumference of the largest cross-sectional portion of the piston, a latch finger pivoted to the trigger lever for movement relative to the trigger lever between latching and unlatching positions and also movable with the trigger lever to unlatching position upon movement of the trigger lever to extended position, an abutment carried by the first body portion engageable with said latch finger when the latter is in latching position and said trigger lever is in retracted position to limit movement of the first body portion toward one of its positions, the pivot axis of said trigger lever and the latch finger both being laterally offset from the engagement between the latch finger and abutment so that force exerted by the motor means urging the first body portion toward said one position also urges the latching finger to latching position and the trigger lever to extended position to move the latch finger out of engagement with the abutment and -movement of the first body portion toward its other position causes movement of the latch finger to unlatching position without movement of the trigger lever to extended position.

movable between first and second positions relative to a second portion to permit and restrict flow from one end "of the piston to the other when the piston is disposed in -a well conduit, motor means urging said first portion from one to the other of its positions responsive to a change in a well condition between said upper and lower levels, and a latching mechanism for releasably holding the first body portion in its first and second positions until the piston arrives respectively at its upper and lower levels including a lever pivoted to the second body portion for movement laterally of the piston between extended and retracted positions respectively without and within the outer circumference of the largest cross-sectional portion of the piston so that the well conduit prevents movement of the lever to extended position while the piston is moving between said two levels, a latch finger pivoted to said lever, said first body portion having opposing abutment surfaces alternately engageable by the latch finger to respectively prevent movement of said first body portion from said one position and from said second position; said lever and latch finger pivots being offset laterally from the abutment surfaces on the first body portion so that with the latch finger in engagement with one of said abutment surfaces and the lever in retracted position, a predetermined force exerted on the first body portion by the motor can pivot the latch finger out of engagement with the first body portion without extending the lever and with the latch finger in engagement with the other of said abutment surfaces, force applied to the first body portion moves the lever to extended position to disengage the latch finger from the first body portion.

12. In a well apparatus wherein there is provided a motor means and also first and second portions movable between two positions relative to each other by said motor 21 means, a latching mechanism holding the first portion in one of its positions and then releasing it for movement to its other position including a part carried by the first portion and movable laterallyrelative to the apparatus between a retracted position and extended position respectively within and without the outer circumference of the largest cross-sectional portion of the well apparatus, and a force transmitting connection between said part and said second portion preventing said relative movement between. the pontions from one to the other of their positions despite force applied by the motor means to cause such movement, said connection transmitting said force to the part to urge it to said extended position and being releasable upon movement of the part to extended position to permit said relative movement,

13. The apparatus of claim 12 wherein a connection is also provided to prevent said relative movement between the portions from said another to said one of their positions, the last mentioned connection being releasable upon thev mot-or means exerting a force of predetermined magnitude urging the first and second portions in their relative movement from said another to said one position.

14. The apparatus of claim 13 wherein the last mentioned connection transmits force from the first portion to said partbefore the connection is released to urge the part to retracted position. p

15. The apparatus, of claim 12 in combination with a second latching mechanism holding the first portion in one of its positions and then releasing it for movement to said one position including a latch forming a releasable connection between said portions when the latter are in their second position to prevent movement to the first position, and a, trigger for said latch movable to disengage the, latch from one of said portions and including a part engageable by an instrumentality exteriorly of the apparatus tomove the trigger to disengage the latch.

16. The apparatus of claim 12 in combination with a second latching mechanism holding the first portion in theother of its positions and then releasing it for movement to its one position including a latch carried by one portion and engageable with the other when the portions are in their second position to prevent movement to the first position, temperature sensitive means connected to said latch to move it to disengage it from said other portion upon the temperature sensitive means being exposed to a temperature of predetermined magnitude.

17. A free piston adapted to reciprocate between upper and lower levels in a well conduit which comprises, in combination, piston body means having a first portion movable between two positions relative to a second portion to permit and restrict flow from one end of the piston to the other when the piston is disposed in a well conduit, motor means generating a force of a magnitude which varies with a change in a well condition towhich the motor means is exposed as the free piston moves between said upper and lower levels, said motor means being connected between said first and second portions to apply said force therebetween to urge said first portion from one to the other of its positions, and a latching mechanism preventing movement of the first portion from said one to the other of its positions while the piston is moving between said upper and lower levels including a releasable latch connecting between said portions upon movement of the first portion to said one position to prevent its movement to said another position, and trigger means connected to the latch to move the latch out to releasing position responsive to movement of the trigger means by i an instrumentality exteriorly of the piston.

18. The piston of claim 17 wherein said trigger means includes a-plunger which in a locking position holds the latch in engagement with said portions and movable to releasing position to permit the latch to move out of such engagement, said plunger when in said locking position extending to the exterior of the piston to engage a stop for moving the plunger to releasing position.

19. A free piston adapted to reciprocate between upper and lower levels. in a well conduit which comprises, in combination, a piston body means having a first portion moveable between two positions relative to a second portion to permit and restrict flow from one end of the piston to the other when the piston is disposed in a well conduit, motor means generating a force of a magnitude which varies with a change in a well condition to which the motor means is exposed as the free piston moves between said upper and lower levels, said motor means being connected between said first and second portions to apply said force therebetween to urge said first portion from one to the other of'its positions, and a latching mechanism preventing movement of the first portion from said one to the other-of its positions while the piston is moving between said upper and lower levels including a releasable lat-ch connected between said portions upon the movement of the first portion to its one position to prevent its movement to said another position, and torn perature sensitive trigger means connected to the latch and operable independently of the motor means to move the latch to release one of the portions upon the temperature sensitivetrigger means being at a temperature of predetermined magnitude.

20. A free piston adapted to reciprocate between upper and lower levels in a well conduit which comprises, in combination, piston body means including flow control means actuatable to prevent and permit flow from one end of the free piston to the othenmotor means generating a force of a magnitude which varies with a change in well condition to which the motor means is exposed as the .free piston moves between said upper and lower levels,

said motor means being connected to said flow control means to apply said force thereto to actuate the flow control means as aforesaid, means carried by the body means engaging one of the motor means and flow control means to prevent actuation of the flow control means by the motor means while the free piston moves from one level to the other and being releasable to permit such actuation responsive to the free pistons arrival at said other level, latch means carried by the body means engaging one of the motor means and control means to prevent actuation of the flow control means by the motor means while the free piston moves from said other to said one level and trigger means having a connection with the latch means and movable to release the latch means to permit such actuation responsive to the free piston striking a stop at said one level in said conduit.

21. The piston of claim 20 wherein the first mentioned actuation preventing means includes a trigger movable between retracted and extended positions respectively within and without the outer circumference of the largest cross-sectional portion of the free piston, and a connec tion between said trigger and one of said motor and flow control means preventing actuation of the latter while the trigger is in retracted position and releasable to permit actuation of the flow control means upon the trigger moving to extended position.

22. The free piston of claim 21 wherein said trigger means includes a movable part exposed for engagement with means carried bv the well conduit to move the part to release the latch upon arrival of the free piston at said one level and engagement of said means carried by the well conduit with said part.

23. A free piston adapted to reciprocate between upper and lower levels in a well conduit which comprises, in

combination, piston body means including flow control 23 trol means by the motor means while the free piston moves from one level to the other and being releasable to permit such actuation responsive to the free pistons arrival at said other level, and means carried by the free piston and preventing actuation of the flow control means by the motor means while the free piston moves from said other to said one level including a latch engageable to resist force applied by the motor means to actuate the flow control means and temperature sensitive means operable independently of the motor means to move the latch to releasing position responsive to the temperature sensitive means being at a predetermined temperature.

24. A free piston adapted to reciprocate between upper and lower levels in a well conduit which comprises, in combination, piston body means having first and second portions, the first portion being movable between two positions relative to the second portion to permit and restrict flow from one end of the piston to the other when the piston is disposed in a well conduit; motor means connected to said first portionto urge the same from one to the other of its positions responsive to a change in a well condition between said upper and lower levels; detent means preventing relative movement between said portions while the free piston is moving in one direction in the well including a trigger part carried by one of the body portions and movable laterally of the free piston between retracted and extended positions such that the well conduit holds the trigger part in retracted position while the free piston is moving between said two levels, a latch connection between said trigger part and the other of said portions preventing movement of the first portion from one to the other of its positions while the trigger part is in retracted position and releasing the first portion upon the trigger part moving to extended position; a latch mechanism carried by one of the portions and engageable with the other portion when the first portion is in said other position; and timing means connected to the latch mecha- 24 nism to release the same upon lapse of a predetermined time interval.

25. The free piston of claim 24 wherein said timing means includes a timing piston reciprocal in a cylinder, a restricted flow passage between opposite ends of said piston to time its movement, and means for releasing the latch mechanism upon the timing piston moving through a predetermined distance.

26. A free piston adapted to reciprocate between upper and lower levels in a well conduit which comprises, in combination, piston body means including flow control means actuatable to limit and permit flow from one end of the free piston to the other, motor means generating a force of a magnitude which varies with a change in well condition to which the motor means is exposed as the free piston moves between said upper and lower levels, said motor means being connected to said flow control means to apply said force thereto to actuate the flow control means as aforesaid, means preventing actuation of the flow control means by the motor means while the free piston moves from one level to the other and being releasable to permit such actuation responsive to the free pistons arrival at said other level, said means preventing actuation also being releasable to permit actuation upon the free piston arriving at said one level, and timing means having a connection with the actuation preventing means for so releasing the actuation preventing means upon the lapse of a predetermined time interval after the free piston leaves said other level.

References Cited in the file of this patent UNITED STATES PATENTS Re. 23,698 Brown Aug. 18, 1953 1,776,889 Claytor Sept. 30, 1930 2,714,855 Brown Aug. 9, 1955 2,789,645 Curnutt et al Apr. 23, 1957 

